We present a measurement of the time-behavior of the divergence of pulsed laser beams, joining the time- resolution capability of photodetectors and the space- resolved information of the knife-edge technique. This method has been tested by using HERCULES, a high output energy XeCl laser facility, equipped with two different unstable resonators. The time-resolved beam divergence was much higher than the time-integrated one at the leading edge of the laser pulse duration, and it had a minimum before the peak of the laser pulse. The consequences on the optimization of laser-matter interaction processes are discussed.
{"title":"Measurement of the time-resolved divergence of pulsed laser beams","authors":"P. Di Lazzaro, F. Flora, N. Lisi","doi":"10.1117/12.316572","DOIUrl":"https://doi.org/10.1117/12.316572","url":null,"abstract":"We present a measurement of the time-behavior of the divergence of pulsed laser beams, joining the time- resolution capability of photodetectors and the space- resolved information of the knife-edge technique. This method has been tested by using HERCULES, a high output energy XeCl laser facility, equipped with two different unstable resonators. The time-resolved beam divergence was much higher than the time-integrated one at the leading edge of the laser pulse duration, and it had a minimum before the peak of the laser pulse. The consequences on the optimization of laser-matter interaction processes are discussed.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127687160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. D. Carpenter, Peter Weber, J. Peter, G. Szabó, T. Szakács, A. Lőrincz
We demonstrate the applicability of a genetic algorithm (GA) to control the focus of an adaptive optical system using a liquid crystal spatial light modulator. The optical setup and the algorithm applied are set to fitness type reinforcement for learning. The particular GA developed optimizes the phase shifts in 32 independent pixels, and is biased towards approximating continuous functions that suit the focusing problem. The learning process is demonstrated to work reliably even in the presence of experimental noise.
{"title":"Self-learning optical system based on a genetic-algorithm driven spatial light modulator","authors":"S. D. Carpenter, Peter Weber, J. Peter, G. Szabó, T. Szakács, A. Lőrincz","doi":"10.1117/12.316567","DOIUrl":"https://doi.org/10.1117/12.316567","url":null,"abstract":"We demonstrate the applicability of a genetic algorithm (GA) to control the focus of an adaptive optical system using a liquid crystal spatial light modulator. The optical setup and the algorithm applied are set to fitness type reinforcement for learning. The particular GA developed optimizes the phase shifts in 32 independent pixels, and is biased towards approximating continuous functions that suit the focusing problem. The learning process is demonstrated to work reliably even in the presence of experimental noise.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"55 27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128363713","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The evolution of the main parameters of the intracavity laser radiation oscillating in a Gaussian-cavity applied to a XeCl laser, has been experimentally investigated. It has been found that the temporal evolution of the main laser beam parameter was well approximated by the evolution of a Shell-Gaussian model beam propagating in a bare Gaussian cavity, even if the intensity profiles of the oscillating radiation were quite affected by XeCl laser gain characteristics.
{"title":"Effects of time evolution of the laser beam parameters in Gaussian cavities","authors":"C. Palma, C. Panzera, M. Perrone, G. De Nunzio","doi":"10.1117/12.316571","DOIUrl":"https://doi.org/10.1117/12.316571","url":null,"abstract":"The evolution of the main parameters of the intracavity laser radiation oscillating in a Gaussian-cavity applied to a XeCl laser, has been experimentally investigated. It has been found that the temporal evolution of the main laser beam parameter was well approximated by the evolution of a Shell-Gaussian model beam propagating in a bare Gaussian cavity, even if the intensity profiles of the oscillating radiation were quite affected by XeCl laser gain characteristics.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126884530","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Tassy, P. Delaporte, B. Fontaine, B. Forestier, M. Sentis, O. Uteza
The uniformity and stability of discharge process in a high pulse repetition frequency long pulse XeCl laser are investigated for three different copper electrode roughnesses in single shot regime and versus PRF. The discharge quality evolution is experimentally analyzed from discharge photographs obtained with CCD video camera and pressure perturbation measurements achieved with a piezoelectric pressure probe placed very close to the discharge volume.
{"title":"Cathode roughness effects in a high-PRF long-pulse XeCl laser","authors":"I. Tassy, P. Delaporte, B. Fontaine, B. Forestier, M. Sentis, O. Uteza","doi":"10.1117/12.316556","DOIUrl":"https://doi.org/10.1117/12.316556","url":null,"abstract":"The uniformity and stability of discharge process in a high pulse repetition frequency long pulse XeCl laser are investigated for three different copper electrode roughnesses in single shot regime and versus PRF. The discharge quality evolution is experimentally analyzed from discharge photographs obtained with CCD video camera and pressure perturbation measurements achieved with a piezoelectric pressure probe placed very close to the discharge volume.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"3423 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130610164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The laser is one of the most fantastic and versatile tool invented recently, although its story began with luminescent phenomena, which have been always at the center of curiosity of mankind since ancient times. However the important aspects of the luminescence have been discovered in the past century, and only in the present one the various basic and technical knowledges coalesced for the realization of the first laser device. Since then the field exploded almost exponentially, and thousands of different materials, in the state of solids, liquids, vapors, gases, plasmas, and elementary particles have lased up to now. However only a few of them became practical lasers, which have been used with outstanding results both in basic science, and in industrial and commercial applications. Due to the vastness ofthe laser field, only the most important aspects will be considered here, starting from the essential historical background, describing the rapid evolution of the main laser systems in the past decades, and trying to forecast the near future developments. In general, although a few sectors show signs of maturity, the field as a whole looks well alive and there will be a new golden age as a consequence of impressive technological advances.
{"title":"Past, present, and future of laser technology","authors":"G. Baldacchini","doi":"10.1117/12.316553","DOIUrl":"https://doi.org/10.1117/12.316553","url":null,"abstract":"The laser is one of the most fantastic and versatile tool invented recently, although its story began with luminescent phenomena, which have been always at the center of curiosity of mankind since ancient times. However the important aspects of the luminescence have been discovered in the past century, and only in the present one the various basic and technical knowledges coalesced for the realization of the first laser device. Since then the field exploded almost exponentially, and thousands of different materials, in the state of solids, liquids, vapors, gases, plasmas, and elementary particles have lased up to now. However only a few of them became practical lasers, which have been used with outstanding results both in basic science, and in industrial and commercial applications. Due to the vastness ofthe laser field, only the most important aspects will be considered here, starting from the essential historical background, describing the rapid evolution of the main laser systems in the past decades, and trying to forecast the near future developments. In general, although a few sectors show signs of maturity, the field as a whole looks well alive and there will be a new golden age as a consequence of impressive technological advances.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"245 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132273272","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Konstantinos N. Halkiotis, L. Manolopoulos, N. Uzunoglou, D. Yova
Photodynamic therapy (PDT) is a promising new treatment for a variety of malignant tumors. Recently, PDT has been investigated as an alternative treatment for pancreatic carcinoma. The selection of photosensitizer and laser light are equally important for the treatment efficacy. The purpose of this study is to evaluate drug and light dose dependence of photodynamic effect in pancreatic cancer cells. Zinc tetrasulfonated phthalocyanines used as photosensitizer and a novel diode laser system terminated at alight shaping diffuser was used as light source. Viability was measured 24 and 72 hours after treatment and almost 100 percent lethality levels were achieved, by using low light doses independently of drug concentration. The results are discussed in correlation with light and drug doses.
{"title":"Drug and light dose dependence of PDT on pancreatic cancer cells in vitro","authors":"Konstantinos N. Halkiotis, L. Manolopoulos, N. Uzunoglou, D. Yova","doi":"10.1117/12.316629","DOIUrl":"https://doi.org/10.1117/12.316629","url":null,"abstract":"Photodynamic therapy (PDT) is a promising new treatment for a variety of malignant tumors. Recently, PDT has been investigated as an alternative treatment for pancreatic carcinoma. The selection of photosensitizer and laser light are equally important for the treatment efficacy. The purpose of this study is to evaluate drug and light dose dependence of photodynamic effect in pancreatic cancer cells. Zinc tetrasulfonated phthalocyanines used as photosensitizer and a novel diode laser system terminated at alight shaping diffuser was used as light source. Viability was measured 24 and 72 hours after treatment and almost 100 percent lethality levels were achieved, by using low light doses independently of drug concentration. The results are discussed in correlation with light and drug doses.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115453113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Delaporte, M. Voitik, B. Fontaine, M. Sentis, O. Uteza
Vacuum ultraviolet fluorescence emissions of alkali rare gas triatomic ionic excimers have been observed. These molecules have been produced by electron beam excitation of rare gas alkali mixtures at high pressure and high temperature. Spectroscopic and kinetic studies have been performed on Kr2+Cs ions which exhibit a spectrum centered at 159nm. Binding energy of the lowest excited state has been estimated. Simple kinetic considerations allowed us to propose two formation processes of these ions and to estimate their rate constant.
{"title":"Spectroscopy of triatomic alkali rare-gas ionic excimers","authors":"P. Delaporte, M. Voitik, B. Fontaine, M. Sentis, O. Uteza","doi":"10.1117/12.316592","DOIUrl":"https://doi.org/10.1117/12.316592","url":null,"abstract":"Vacuum ultraviolet fluorescence emissions of alkali rare gas triatomic ionic excimers have been observed. These molecules have been produced by electron beam excitation of rare gas alkali mixtures at high pressure and high temperature. Spectroscopic and kinetic studies have been performed on Kr2+Cs ions which exhibit a spectrum centered at 159nm. Binding energy of the lowest excited state has been estimated. Simple kinetic considerations allowed us to propose two formation processes of these ions and to estimate their rate constant.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127460821","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Serafetinides, A. Papayannis, E. Fabrikesi, K. Rickwood, You Wang, Yi-Wei Shi, M. Miyagi, N. Croitoru, J. Harrington, R. K. Nubling
In the last few years, there has been an increasing interest for the 3.0 micrometers laser radiation, as this wavelength is very strongly absorbed by the water and the other components of soft and hard tissue, in various medical applications, as soft tissue treatment, atherosclerotic plagues removal, treatment of eye lenses, vitreous surgery, hard tissue treatment, bone cutting and drilling, dentistry applications, etc. For all these medical applications reliable lasers emitting in the 3.0 micrometers wavelength range are needed and thus an intensive development effort is going on throughout the world. Our laser development effort, with the Er:YAG and the HF lasers, the only lasers emitting in the 3.0 micrometers wavelength part of the spectrum, in N.T.U.A., is briefly described in this article. For each one of the above possible medical applications, a demand for good flexible delivery systems, for pulsed Er:YAG or continuous wave and pulsed HF laser radiation arises. Several research groups around the world have suggested some possible solutions and among them are sapphire fibers, zirconium fluoride glasses, hollow metallic waveguides, hollow dielectric waveguides, hollow plastic waveguides, etc. In this paper we present the transmission properties of dielectric coated silver hollow glass waveguides fabricated in Japan, dielectric coated quartz waveguides and hollow plastic waveguides fabricated in Israel, sapphire fibers fabricated in USA, and fluoride glass fibers fabricated in France, we compare their straight and bent loss characteristics and we discuss their potential in the above mentioned medical applications.
{"title":"Lasers, waveguides and fibers for 3.0-μm medical applications","authors":"A. Serafetinides, A. Papayannis, E. Fabrikesi, K. Rickwood, You Wang, Yi-Wei Shi, M. Miyagi, N. Croitoru, J. Harrington, R. K. Nubling","doi":"10.1117/12.316632","DOIUrl":"https://doi.org/10.1117/12.316632","url":null,"abstract":"In the last few years, there has been an increasing interest for the 3.0 micrometers laser radiation, as this wavelength is very strongly absorbed by the water and the other components of soft and hard tissue, in various medical applications, as soft tissue treatment, atherosclerotic plagues removal, treatment of eye lenses, vitreous surgery, hard tissue treatment, bone cutting and drilling, dentistry applications, etc. For all these medical applications reliable lasers emitting in the 3.0 micrometers wavelength range are needed and thus an intensive development effort is going on throughout the world. Our laser development effort, with the Er:YAG and the HF lasers, the only lasers emitting in the 3.0 micrometers wavelength part of the spectrum, in N.T.U.A., is briefly described in this article. For each one of the above possible medical applications, a demand for good flexible delivery systems, for pulsed Er:YAG or continuous wave and pulsed HF laser radiation arises. Several research groups around the world have suggested some possible solutions and among them are sapphire fibers, zirconium fluoride glasses, hollow metallic waveguides, hollow dielectric waveguides, hollow plastic waveguides, etc. In this paper we present the transmission properties of dielectric coated silver hollow glass waveguides fabricated in Japan, dielectric coated quartz waveguides and hollow plastic waveguides fabricated in Israel, sapphire fibers fabricated in USA, and fluoride glass fibers fabricated in France, we compare their straight and bent loss characteristics and we discuss their potential in the above mentioned medical applications.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125908989","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The point to point telecommunication in the atmosphere with laser signals using the existing optoelectronic technology is an option of the modern communications design. An optical link is strong depending on the optoelectronic hardware parameters and to the topology or to the environment of the applications area. Many laser-links are already fabricated for use in military or in commercial applications. Main advantages are the freedom from licenses, the RFI-EMI immunity, the wide bandwidth and the information security. Main disadvantages are the atmospheric steady and variable attenuation, the radiation hazards and in some cases the material cost. Based on this know-how we describe in this paper the more important broadcasting parameters of radio- TV-teletext programs with laser beams, starting from the atmospheric transmission influence, continuing with a laser selection guide and with some broadcasting electronic techniques and ending with the proposed modification of a coherent laser-link to a new active receiver system which fulfill normal or special laser broadcasting options. Possible applications of our study may be the point to multi-point optical communications for local pay TV, the allocation of optical bands for broadcasting, the radii of cellular laser broadcasting, the simulcasting with laser and RF carriers, the implementations of an interactive Radio and TV, etc.
{"title":"Free atmospheric broadcasting of radio, TV and teletext with laser radiation","authors":"S. Tsitomeneas, E. Voglis","doi":"10.1117/12.316599","DOIUrl":"https://doi.org/10.1117/12.316599","url":null,"abstract":"The point to point telecommunication in the atmosphere with laser signals using the existing optoelectronic technology is an option of the modern communications design. An optical link is strong depending on the optoelectronic hardware parameters and to the topology or to the environment of the applications area. Many laser-links are already fabricated for use in military or in commercial applications. Main advantages are the freedom from licenses, the RFI-EMI immunity, the wide bandwidth and the information security. Main disadvantages are the atmospheric steady and variable attenuation, the radiation hazards and in some cases the material cost. Based on this know-how we describe in this paper the more important broadcasting parameters of radio- TV-teletext programs with laser beams, starting from the atmospheric transmission influence, continuing with a laser selection guide and with some broadcasting electronic techniques and ending with the proposed modification of a coherent laser-link to a new active receiver system which fulfill normal or special laser broadcasting options. Possible applications of our study may be the point to multi-point optical communications for local pay TV, the allocation of optical bands for broadcasting, the radii of cellular laser broadcasting, the simulcasting with laser and RF carriers, the implementations of an interactive Radio and TV, etc.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"91 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114454107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Long-wavelength vertical-cavity surface-emitting semiconductor lasers are investigated and heating effects on the light vs. current characteristics of VCSELs are analyzed by thermal-electric, optical, and electronic modeling. The model includes nonuniform current injection, carrier diffusion, stimulated emission, distributed heat sources, and active material band structure calculations. Device parameters such as threshold current, and external quantum efficiency are evaluated. Simulated power vs. current characteristics exhibit the typical thermal roll-over in continuous wave operation. The model is applied to two specific optimized underetched structure designs in order to provide an understanding of the current-funneling mechanism and the thermal limitations of such devices.
{"title":"Numerical modeling of long-wavelength vertical-cavity surface-emitting semiconductor lasers. I. Continuous-wave modeling","authors":"A. Tsigopoulos, V. Paschos, P. Salet, J. Jacquet","doi":"10.1117/12.316558","DOIUrl":"https://doi.org/10.1117/12.316558","url":null,"abstract":"Long-wavelength vertical-cavity surface-emitting semiconductor lasers are investigated and heating effects on the light vs. current characteristics of VCSELs are analyzed by thermal-electric, optical, and electronic modeling. The model includes nonuniform current injection, carrier diffusion, stimulated emission, distributed heat sources, and active material band structure calculations. Device parameters such as threshold current, and external quantum efficiency are evaluated. Simulated power vs. current characteristics exhibit the typical thermal roll-over in continuous wave operation. The model is applied to two specific optimized underetched structure designs in order to provide an understanding of the current-funneling mechanism and the thermal limitations of such devices.","PeriodicalId":373160,"journal":{"name":"GR-I International Conference on New Laser Technologies and Applications","volume":"81 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129032780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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